ANALISIS TINGGI MUKA AIR BANJIR SEBAGAI DASAR PENETAPAN BATAS SEMPADAN SITU TERATE, KABUPATEN SERANG, BANTEN

Situ, a term used in Indonesia for small natural lakes, plays an important role in maintaining ecosystem balance and supporting the sustainability of water resources. In addition to functioning as a water storage body, a situ also serves as a water conservation area, flood control facility, groundwater recharge zone, raw water source, irrigation water supply, freshwater fish habitat, and recreational area. Delineation of the situ waterbody boundary is an essential step in protecting its ecological functions and controlling land use development in the surrounding area. This study aims to determine the flood water level (FWL) of Situ Terate as a basis for defining the waterbody boundary. The determination of the flood water level was conducted through the integration of hydrological analysis, hydraulic modeling, and verification using historical flood information. The data used in this study consisted of DEMNAS (Indonesian National Digital Elevation Model), rainfall records for the period 2015–2024, and historical flood information obtained through field surveys and community interviews. Spatial analysis was performed using ArcGIS to delineate the catchment area and derive its hydrological characteristics, while hydraulic modeling was carried out using HEC-RAS 2D with design flood hydrographs generated by the HSS Nakayasu  method. The results indicate that the simulated water surface elevation corresponding to the 50-year return period flood (Q50) was +17.107 m above mean sea level (amsl), which closely matched the historical flood elevation of +17.11 m amsl. Based on this verification, the flood water level of Situ Terate was established at +17.11 m amsl, resulting in a waterbody area of 22.10 ha. The findings of this study can be used as a basis for delineating the situ waterbody boundary and as supporting information for the establishment of the Situ Terate buffer zone in accordance with the applicable regulations.